Multiple Endocrine Neoplasia Syndromes
What is it?
Multiple endocrine neoplasia (MEN) syndromes affect the thyroid and other endocrine glands that produce hormones in the body. MEN has previously been known as familial endocrine
adenomatosis. There are three forms of MEN: MEN1 (Wermer's syndrome), MEN2A
(Sipple syndrome), and MEN2B (previously known as MEN3). Each tends to cause excessive growth of cells, called
hyperplasia, and tumors in a number of endocrine glands.
Who gets it?
Each MEN syndrome is an autosomal dominant genetic condition. Autosomal refers to a chromosome that is not a sex chromosome. For all types of MEN, the children of an affected individual have a 50% chance of inheriting the defective gene.
What causes it?
MEN1 is caused by mutation at the PYGM gene, one of a group of tumor suppressor genes. If you inherit one defective copy of a tumor suppressor gene from either parent, there's a high probability of having a second mutation in at least one dividing cell. Then, that cell no longer possesses even one normal copy of the gene. When both copies are defective, tumors develop.
Both types of MEN2 are caused by mutations in the RET gene. A mutation in only one copy of the RET gene is enough to cause the disease.
What are the symptoms?
MEN1 patients will have hyperplasia or tumors of several endocrine glands, including the
parathyroids, the pancreas, and the pituitary. The most common symptom of MEN1 is
hyperparathyroidism, which leads to elevated blood calcium levels, kidney stones, weakened bones, and depression of the nervous system. Almost all MEN1 patients show parathyroid symptoms by age 40. The anterior pituitary and the adrenal glands can also be affected. The thyroid gland is rarely involved in MEN1 symptoms.
Patients with MEN2A and MEN2B will have two main symptoms-medullary thyroid cancer
(MTC) and a tumor of the adrenal gland medulla known as pheochromocytoma. While MTC is a slow-growing cancer, it can be cured in less than 50% of the cases. Pheochromocytoma is usually a benign tumor that causes excessive secretion of adrenal hormones, which, in turn, can cause life-threatening hypertension and cardiac arrhythmia. MEN2A patients are more likely to increase in size (hypertrophy) and develop tumors of the parathyroid gland, although less than 20% will show parathyroid involvement.
MEN2B patients are also characterized by swollen lips; tumors of the mucous membranes of the eye, mouth, tongue, and nasal cavity; enlarged colon; and skeletal abnormalities. Symptoms develop early in life, often under five years of age.
How is it diagnosed?
Diagnosis of MEN is based on clinical features and on testing for elevated hormone levels. For MEN1, your doctor will check the parathyroid. For both types of MEN2, physician's can detect medullary thyroid cancer
(MTC) by measuring levels of the thyroid hormone calcitonin. Many other hormone levels can be measured to determine the involvement of the various other endocrine glands. Doctors have been able to diagnose both MEN1 and MEN2 since 1994 through genetic screening using DNA technology. Your doctor can diagnose MEN2B by physical examination alone. However, MEN2A can only be identified by measuring hormone levels or by finding endocrine tumors.
What is the treatment?
No complete treatment is available for genetic conditions such as MEN. However, some of the outcomes and symptoms of MEN can be treated. For example, pheochromocytoma in both types of MEN2 can be cured by surgically removing the tumor. Medullary thyroid cancer
(MTC) can be treated and even prevented by removing the thyroid. After
thyroidectomy, you will receive normal levels of thyroid hormone orally or by injection. If MTC has spread (metastasized), however, chemotherapy and radiation therapy will not control the further metastasis of the disease.
Children who are identified as carriers of the RET gene can be offered total thyroidectomy to prevent the development of
MTC.
Self-care tips
There is no preventive measure to block the genetic mutations such as those that cause MEN. However, when diagnosed early, the outlook is reasonably good, even for MEN2B, the most dangerous of the three forms. Even without treatment, a few individuals with MEN2A mutations will never show any symptoms at all. By analyzing at-risk family members using molecular genetic techniques, physicians can provide earlier treatment and improved outcomes.
This information has been designed as a comprehensive and quick reference
guide written by our health care reviewers. The health information written
by our authors is intended to be a supplement to the care provided by your
physician. It is not intended nor implied to be a substitute for
professional medical advice.
|
